What is the optimal blood glucose level to maintain in critically ill patients, particularly those in the Intensive Care Unit (ICU) with or without a history of diabetes?

Blood Glucose Management in the ICU

For critically ill ICU patients, maintain blood glucose between 140-180 mg/dL (7.8-10.0 mmol/L), initiating insulin therapy when glucose persistently exceeds 180 mg/dL. 1

When to Start Insulin Therapy

• Initiate insulin when blood glucose is ≥180 mg/dL (10.0 mmol/L), confirmed on two separate measurements. 1, 2
• This threshold applies to all critically ill ICU patients, regardless of diabetes history. 1
• Do not wait for glucose to reach 300 mg/dL or higher before treating—this is a common error. 3

Target Blood Glucose Range

The standard target for most ICU patients is 140-180 mg/dL (7.8-10.0 mmol/L). 1, 2

This recommendation is based on the landmark NICE-SUGAR trial, which demonstrated that intensive glucose control (targeting 80-110 mg/dL) resulted in:

• 27.5% mortality versus 25% with moderate control 1
• 10-15 fold higher rates of hypoglycemia 1
• Increased overall mortality with aggressive targets 1

More Stringent Targets (110-140 mg/dL)

Consider tighter control (110-140 mg/dL) only for highly selected patients: 1

• Critically ill patients undergoing cardiac or major surgery 1
• Patients with previously excellent outpatient glycemic control 1
• Only if this can be achieved without significant hypoglycemia risk 1

Insulin Delivery Method

• Use continuous intravenous insulin infusion for all critically ill ICU patients requiring glycemic control. 1, 2
• Employ a validated computerized or written insulin protocol that has demonstrated safety and efficacy. 1, 4
• Avoid sliding-scale insulin alone—it is strongly discouraged and associated with poor outcomes. 1, 2, 3

Glucose Monitoring Frequency

• Monitor glucose every 30 minutes to 2 hours when using IV insulin therapy. 1
• For patients not on IV insulin but requiring monitoring, check every 4-6 hours. 1, 2
• Use FDA-approved point-of-care hospital-calibrated glucose meters, not standard bedside meters. 1

Critical Pitfalls to Avoid

Never target glucose <110 mg/dL in general ICU populations—this increases mortality. 1, 4

The evidence is unequivocal: aggressive glucose lowering below 110 mg/dL causes harm through:

• Increased hypoglycemia episodes (even mild hypoglycemia <80 mg/dL increases mortality) 5
• Higher cardiovascular mortality 1
• Longer ICU length of stay 5

Monitor and aggressively correct potassium levels: 2, 4

• Do not start insulin if potassium <3.3 mEq/L 4
• Hypokalemia occurs in approximately 50% of patients during insulin treatment 4
• Severe hypokalemia (<2.5 mEq/L) significantly increases mortality 4

Ensure adequate nutrition protocols are in place: 1, 6

• Hypocaloric feeding, particularly in the first week, can complicate glucose management 1
• Coordinate insulin dosing with nutritional intake 6

Special Considerations

For patients with pre-existing diabetes: 6

• The same 140-180 mg/dL target applies 6
• These patients do not benefit from glucose reduction to the same extent as non-diabetics 6
• They face the same hypoglycemia risks, so avoid aggressive targets 6

When transitioning from IV to subcutaneous insulin: 2, 4

• Administer basal subcutaneous insulin 1-2 hours before stopping IV infusion 2, 4
• Calculate basal dose as 60-80% of total daily IV insulin requirement 4
• Never stop IV insulin abruptly—this causes rebound hyperglycemia 4

Monitoring for Complications

• Track all hypoglycemic episodes (<70 mg/dL) in the medical record. 1
• Implement a hospital-wide hypoglycemia management protocol. 1
• Monitor for signs of cerebral edema if rapid glucose changes occur, especially in younger patients. 4
• Assess mental status changes that may indicate iatrogenic complications. 4